Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $162.52   11.751%   $181.6177   $181.62   $181.60   $181.60  
  Purchase #2 $39.94   11.599%   $44.5726   $44.57   $44.55   $44.60  
  Purchase #3 $55.38   10.536%   $61.2148   $61.21   $61.20   $61.20  
  Purchase #4 $95.58   9.724%   $104.8742   $104.87   $104.85   $104.90  
  Purchase #5 $126.87   11.508%   $141.4702   $141.47   $141.45   $141.50  
  Purchase #6 $179.73   8.658%   $195.291   $195.29   $195.30   $195.30  
  Purchase #7 $201.60   10.205%   $222.1733   $222.17   $222.15   $222.20  
  7 purchase totals = $861.62       $951.2138   $951.20   $951.10   $951.30